It is well known that the transportation and storage of hydrocarbons can be a hazardous affair. Crude oil is often transported via tanker vessel or tanker truck and, on occasion, vehicles carrying oil have met some calamity which resulted in the spillage of the cargo oil. It is estimated that between 30 to 40 oil tankers a year accidently release significant amounts of crude oil into the environment. At sea, the spilled oil tends to form floating oil slicks which kill fish and fowl alike. When on land, the spilled oil has a tendency to seep into the soil and contaminate ground water. In either case, the liquid oil is difficult and expensive to remove from the site of the accident.
Various methods, both physical and chemical, have been used to contain spills and to facilitate oil removal from the surface of water. A physical containment method commonly used is to encircle an oil slick with a floating boom and then scoop up the oil. Drawbacks to this method are that oil slicks tend to spread rapidly so that the slicks must be scooped up in sections and this requires considerable manpower and equipment. Obvious difficulties encountered due to high winds and rough seas will be apparent to those skilled in the art. This method is also impracticable for spills occurring far from shore.
Various chemical schemes have been proposed to clean up large surface area oil spills have been proposed. Sohnius (U.S. Pat. No. 3,607,741) discloses recovery of oil from water using cellulosic material pre-treated to render it hydrophobic to provide it with an affinity for oil. In one embodiment the cellulosic material is contained in a mesh netting to be placed on the surface of the oil. In another embodiment the cellulosic material is contained on the surface of a cylinder which rolls under wind power across an oil slick confined by a boom and entrains oil in this way. Disadvantages of this method are the need for large numbers of booms and cylinders for cleaning up large slicks. The recovery of oil from the cellulosic material would be both time consuming and expensive.
Alquist (U.S. Pat. No. 3,785,972) discloses cleaning up oil slicks by spraying a wax onto the surface of the oil slick in order to increase the liquefaction temperature of the oil above the temperature of the water thereby forming a solid mass which can be scooped up. Wax/hydrocarbon mixtures are also sprayed onto the oil slick and then ignited to burn off the lighter hydrocarbons in the crude thereby forming a hardened, asphalt-like material which is then scooped up. Bartha (U.S. Pat. No. 5,112,495) discloses spraying molten hydrocarbon wax onto the surface of an oil slick whereupon cooling the oil/wax forms a solid mass which may then be physically scooped up.
Drawbacks to these various schemes are that the application of the containment agent to the spilled oil can be costly and time consuming, and spills often occur in remote locations difficult to reach in a short time. Large amounts of wax must be transported to the spill site, heated to the liquid form and then sprayed over the entire surface of the oil slick thus requiring specialized ships and equipment. Further, to transport the large volume of solid mixture from the spill site will require large tanker ships specially adapted with the handling and loading facilities needed to scoop up and store the solid mass.
In order to minimize the chance of an oil spill, emphasis has been placed in the building of safer and stronger transportation vessels. The development of the double hulled oil tanker is an example of one such vessel. These vessels, while decreasing the chance of an oil spill by decreasing the likelihood that the compartment or container holding the oil will be ruptured, tend to be very expensive. Furthermore, no vessel is completely safe from disaster and it is possible that a sufficiently violent calamity may result in the rupture of even the strongest vessel.
The economic costs associated with bulk shipping of crude oil has increased steadily with the higher frequency of marine disasters in recent years. The insurance costs alone associated with underwriting oceanic transport of crude oil are in the tens of millions of dollars at least. It is therefore desirable to provide a method of pre-treating hydrocarbons prior to shipping which will significantly reduce the chances of oils slicks forming in the event of a mishap.
In a related matter, the storage of waste oil and hazardous hydrocarbon compounds such as PCBs (polychlorinated biphenyls), is also problematic. Usually the hydrocarbon is placed in a steel drum or barrel and then stored in a waste storage facility or buried underground. The drums used to store the hydrocarbon sometimes develop defects as a result of corrosion or as a result of an impact. These defects may result in the release of the hazardous compound causing soil and ground water contamination. The leaked hydrocarbon is difficult to clean up, often requiring the soil to be dug up and removed. Efforts have been made to strengthen the storage drums in order to lessen the probability of a leak. These superior drums tend to be expensive.
Another approach in the storage of waste oil and hazardous hydrocarbon compounds is to render the material solid. In the solid state, the consequences of a leak are less serious. The spilled hydrocarbon is easier to collect if it is in the solid state, and the solidified hydrocarbon is less likely to leach into the soil or contaminate the ground water. To solidify the hydrocarbon, a solidifying agent is added in sufficient concentration to render the mixture a solid or semi-solid mass. The solidifying agents normally used tend to be expensive, and the solidifying process is often difficult or expensive to reverse. Weitzen (U.S. Pat. No. 4,341,078) discloses the solidification of PCBs by the addition of a slurry of cryogenically comminuted polymer particles suspended in a cryogenic liquid such as liquid nitrogen. It can be appreciated that the solidifying agent used in Weitzen is expensive and requires specialized equipment to handle. The solid resulting from the Weitzen method is difficult to liquify, requiring ionizing radiation or conditions of high shear. Derby (U.S. Pat. No. 3,881,295) discloses the solidification of PCBs by the addition of swellable polymer particles. The polymer particles imbibe the PCBs and swell to form a thick gel. Derby does not disclose a method of reversing the solidification of the PCB mixture. The reversibility of the solidification step is desirable to ease the disposal of the hazardous material by incineration.